Drop template export semver compat with versions prior to 0.12.1 (retry)

We want to update all our tests to use the new syntax. That means we must bump the tests' old version of d-d to 0.12.1. That means we're not testing compatibility with earlier versions.

This is a revised version of !429 (merged) which gitlab tricked me into merging despite a CI failure. I have rewritten the bottom commit so we get a full every-commit test on this branch.

I intend to get CI to pass on this, and then merge it. I think the merge will be treesame to this MR tip, but I will check.

tests/directly/check_semver_check.rs

@@ -135,9 +135,13 @@ fn read_changelog(
 }
 
 fn check_1(tv: &TrackedVersion, exp: Result<(), ()>) {
-    let got_full = macros::semver::template_export_semver_check_func_macro(
-        quote! { #tv }, //
-    );
+    let got_full = if tv.v.0 == "UNRELEASED" {
+        Ok(quote!(UNRELEASED OK))
+    } else {
+        macros::semver::template_export_semver_check_func_macro(
+            quote! { #tv }, //
+        )
+    };
     let got_abbrev = got_full.as_ref().map_err(|_| ()).map(|_| ());
     eprintln!("{:25} {} exp={exp:?} got={got_abbrev:?}", tv.why, tv.v);
     assert_eq!(got_abbrev, exp, "at={} v={} got={got_full:?}", tv.why, tv.v);